package com.example.utils;

import org.apache.commons.codec.digest.DigestUtils;  
import java.io.File;  
import java.io.FileInputStream;  
import java.io.FileNotFoundException;  
import java.io.IOException;  
import java.nio.MappedByteBuffer;  
import java.nio.channels.FileChannel;  
import java.security.MessageDigest;  
import java.security.NoSuchAlgorithmException;  
import java.util.zip.CRC32;  
  
public class FileSafeCode {  
    /** 
     * 计算大文件 md5获取getMD5(); SHA1获取getSha1() CRC32获取 getCRC32() 
     */  
    protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6',  
            '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };  
    public static MessageDigest messagedigest = null;;  
  
    /** 
     * 对一个文件获取md5值 
     *  
     * @return md5串 
     * @throws NoSuchAlgorithmException 
     */  
    public static String getMD5(File file) throws IOException,  
            NoSuchAlgorithmException {  
  
        messagedigest = MessageDigest.getInstance("MD5");  
        FileInputStream in = new FileInputStream(file);  
        FileChannel ch = in.getChannel();  
        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0,  
                file.length());  
        messagedigest.update(byteBuffer);  
        return bufferToHex(messagedigest.digest());  
    }  
  
     /**  
     * @param target 字符串 求一个字符串的md5值 
     * @return md5 value 
     */  
    public static String StringMD5(String target) {  
        return DigestUtils.md5Hex(target);  
    }  
      
    /*** 
     * 计算SHA1码 
     *  
     * @return String 适用于上G大的文件 
     * @throws NoSuchAlgorithmException 
     * */  
    public static String getSha1(File file) throws OutOfMemoryError,  
            IOException, NoSuchAlgorithmException {  
        messagedigest = MessageDigest.getInstance("SHA-1");  
        FileInputStream in = new FileInputStream(file);  
        FileChannel ch = in.getChannel();  
        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0,  
                file.length());  
        messagedigest.update(byteBuffer);  
        return bufferToHex(messagedigest.digest());  
    }  
  
    /** 
     * 获取文件CRC32码 
     *  
     * @return String 
     * */  
    public static String getCRC32(File file) {  
        CRC32 crc32 = new CRC32();  
        // MessageDigest.get  
        FileInputStream fileInputStream = null;  
        try {  
            fileInputStream = new FileInputStream(file);  
            byte[] buffer = new byte[8192];  
            int length;  
            while ((length = fileInputStream.read(buffer)) != -1) {  
                crc32.update(buffer, 0, length);  
            }  
            return crc32.getValue() + "";  
        } catch (FileNotFoundException e) {  
            e.printStackTrace();  
            return null;  
        } catch (IOException e2) {  
            e2.printStackTrace();  
            return null;  
        } finally {  
            try {  
                if (fileInputStream !=null )  
                    fileInputStream.close();  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
    }  
  
    public static String getMD5String(String s) {  
        return getMD5String(s.getBytes());  
    }  
  
    public static String getMD5String(byte[] bytes) {  
        messagedigest.update(bytes);  
        return bufferToHex(messagedigest.digest());  
    }  
  
    /** 
     * @Description 计算二进制数据 
     * @return String 
     * */  
    private static String bufferToHex(byte bytes[]) {  
        return bufferToHex(bytes, 0, bytes.length);  
    }  
  
    private static String bufferToHex(byte bytes[], int m, int n) {  
        StringBuffer stringbuffer = new StringBuffer(2 * n);  
        int k = m + n;  
        for (int l = m; l < k; l++) {  
            appendHexPair(bytes[l], stringbuffer);  
        }  
        return stringbuffer.toString();  
    }  
  
    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {  
        char c0 = hexDigits[(bt & 0xf0) >> 4];  
        char c1 = hexDigits[bt & 0xf];  
        stringbuffer.append(c0);  
        stringbuffer.append(c1);  
    }  
  
    public static boolean checkPassword(String password, String md5PwdStr) {  
        String s = getMD5String(password);  
        return s.equals(md5PwdStr);  
    }  
}  